Dengue Fever

Dengue fever, also known as breakbone fever, is a mosquito-borne disease primarily found in tropical and subtropical regions. It is caused by the dengue virus, which is transmitted by several species of female mosquitoes of the Aedes genus, particularly Aedes aegypti.

Signs and Symptoms

The majority of dengue infections are asymptomatic or result in only mild symptoms. When symptoms do appear, they typically manifest 3 to 14 days after exposure. Common symptoms include a sudden-onset fever, headache (often behind the eyes), muscle and joint pains, nausea, vomiting, swollen glands, and a characteristic rash. Severe dengue, previously known as dengue hemorrhagic fever, can cause severe abdominal pain, persistent vomiting, rapid breathing, bleeding gums or nose, fatigue, restlessness, blood in vomit or stool, extreme thirst, pale and cold skin, and feelings of weakness.

The clinical course of dengue fever is divided into three phases: febrile, critical, and recovery. The febrile phase involves high fever and generalised pain, lasting two to seven days. Severe cases can progress to a critical phase with plasma leakage, leading to shock, internal bleeding, and organ failure. The recovery phase lasts two to three days, often accompanied by severe itching and a slow heart rate.

Cause and Transmission

Dengue virus (DENV) is an RNA virus belonging to the Flaviviridae family, which also includes yellow fever and Zika viruses. There are four serotypes of the dengue virus (DENV-1, DENV-2, DENV-3, and DENV-4), and infection with one serotype provides lifelong immunity only to that serotype.

Infection is primarily spread through the bite of infected Aedes mosquitoes. The mosquitoes become infected when they bite a person during their viraemic period, and they can then transmit the virus to other humans. Dengue can also be transmitted through infected blood products, organ donation, and from mother to child during pregnancy or birth.

Diagnosis

Diagnosing dengue involves clinical evaluation and laboratory tests. Blood tests can confirm the presence of dengue virus by detecting viral RNA or antibodies. During the first few days of infection, enzyme-linked immunosorbent assay (ELISA) can detect the NS1 antigen. Anti-dengue IgM antibodies become reliably detectable after four or five days. Nucleic acid amplification tests provide the most accurate diagnosis.

Treatment

There is no specific antiviral treatment for dengue fever. Mild cases require supportive care, including pain relief with acetaminophen and fluid intake. Severe dengue necessitates hospitalisation, with treatments such as intravenous fluids and blood transfusions.

Prevention

Preventing dengue involves reducing mosquito exposure and habitats. This includes wearing protective clothing, using mosquito nets and repellents, and eliminating standing water where mosquitoes breed. Two dengue vaccines are available: Dengvaxia, which is recommended for those previously infected, and Qdenga, suitable for individuals aged four years and older.

Epidemiology

Dengue is endemic in more than 100 countries, primarily affecting the Americas, Southeast Asia, and the Western Pacific. The disease is hyperendaemic in areas where multiple serotypes circulate, increasing the risk of severe infections. The incidence of dengue has increased tenfold between 2010 and 2019, partly due to urbanisation, population growth, and climate change.

History

Dengue fever has been recorded since the Jin Dynasty in China (266–420 AD). The principal mosquito vector, Aedes aegypti, spread globally due to the slave trade and international trading from the 15th to the 19th centuries. Severe forms of the disease were first reported in the mid-20th century, and the prevalence of dengue has continued to rise in the 21st century due to urbanisation and climate change.

The term "dengue" is derived from the Kiswahili word dinga, meaning "cramp-like seizure," and was adapted into Spanish and English in the 19th century. The disease was historically known as "breakbone fever" due to its severe muscle and joint pains.

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Self-assessment MCQs (single best answer)

What is the primary vector for the transmission of dengue fever?

Which phase of dengue fever is characterised by high fever and generalised pain?

How many serotypes of the dengue virus are there?

Which of the following is NOT a common symptom of dengue fever?

Which laboratory test is most accurate for diagnosing dengue fever?

What is the recommended treatment for mild cases of dengue fever?

Which vaccine is recommended for individuals aged four years and older to prevent dengue?

How is dengue fever primarily spread?

Which of the following is NOT a method to prevent dengue fever?

From which language is the term "dengue" derived?